Due to the complexity of multiple spindle mechanisms of the kind employed in automatic screw machines and the like, difficult problems of lubrication are presented. The following patents are representative of efforts that have been made in the past to achieve effective lubrication:
______________________________________ U.S. No. 1,125,031 U.S. No. 3,351,392 U.S. No. 2,245,105 U.S. No. 4,068,740 U.S. No. 2,379,944 U.S. No. 4,344,507 U.S. No. 2,625,448 U.S. No. 4,905,794 U.S. No. 2,728,414 Canada No. 0473189 ______________________________________
In U.S. Pat. No. 5,205,376, Nowak provides a system by which a multiple-spindle mechanism is lubricated, and is protected against the entry of foreign matter, by a mist of oil which is distributed under pressure between mutually contacting bearing surfaces, and is discharged outwardly thereof. The mechanism is especially suited for use in an automatic screw machine.
Despite the foregoing, a need exists for an improved system by which all spindles of a multiple-spindle mechanism are simultaneously and continuously lubricated, and it is therefore the broad object of the present invention to provide such a system and a mechanism and machine embodying and incorporating the same.
A more specific object of the invention is to provide such a system by which lubrication of lower position spindles may be favored.
Additional objects of the invention are to provide a mechanism and machine having the foregoing features and advantages, which are relatively incomplex and especially well suited for use in and as a multiple-spindle automatic screw machine, and which help to extend the useful life of the spindles and other components and to ensure smooth and trouble-free operation.
It has now been found that certain of the foregoing and related objects of the invention are attained in a multi-spindle mechanism that includes a housing having a forward journal portion with a circular internal bearing surface; a revolving head mounted for rotation in the housing and comprising a front boss having a circumferential external bearing surface in contact with the internal bearing surface of the housing, and a multiplicity of spindle bearings mounted at locations spaced about the front boss, each of the spindle bearings having an internal bearing surface; a multiplicity of spindles, each rotatably mounted in an associated one of the spindle bearings and having a cylindrical external bearing surface in contact with the internal bearing surface of the associated bearing; and means for supplying liquid lubricant to at least certain of the bearing surfaces in contact with one another. A continuous groove circumscribes the front boss of the revolving head, and a multiplicity of oil ducts operatively connect the internal bearing surface of each spindle bearing to the circumscribing groove. The means for supplying lubricant communicates with the circumscribing groove of the head through a passage in the housing in which the head is mounted, which passage opens onto the circumferential external bearing surface at the entrance to the groove formed into the boss. The opening from the passage has a "first" area, and encompasses a circumferential portion of the groove entrance, which portion has a "second" area that is substantially smaller than the "first" area (by virtue of the narrowness of the groove). In addition, the smallest cross section along the length of each of the connecting oil ducts has a "third" area that is at least as large as the "second" area, and preferably substantially larger. Most desirably, the "third" area will have a value equal to about 40% to 60% of the value of the "first" area, and the "second" area will have a value equal to about 40% to 60% of the value of the "third" area.
The duct connecting the internal surface of each of the spindle bearings to the groove in the head boss will generally comprise two sections lying sequentially along a radius from the axis of rotation of the associated spindle, one duct section extending through the boss and the other extending through the spindle bearing. Each duct section will typically have a substantially uniform cross section along substantially its entire length, with the cross section of the more outward of the duct sections having the "third" area and with the cross section of the more inward duct section having a "fourth" area that is larger than the "third" area; the "fourth" area will desirably have a value substantially equal to that of the "first" area.
In most instances the housing will include a rearward journal portion with a "second" circular internal bearing surface coaxial with the first-mentioned circular internal bearing surface, and the head will have a rear boss with a circumferential external bearing surface in contact with the "second" internal bearing surface. A "second" continuous groove will be formed into the circumferential external bearing surface of the rear boss, and at least one duct will operatively connect the internal bearing surface of each of the rear boss spindle bearings to the "second" circumscribing groove. A "second" passage operatively connected to the lubricant supplying means will open onto the circumferential external bearing surface of the rear boss, and will encompass a circumferential portion of the entrance to the "second" circumscribing groove. In such an embodiment of the mechanism, the encompassed circumferential portion of the "second" groove entrance will also have an area that is substantially smaller than the area of the opening from the "second" passage.
The invention is applied to greatest advantage in mechanisms in which the spindles reciprocate linearly on their axes of rotation, which axes will normally be equiangularly spaced and parallel to the axis of head rotation. Most desirably, the mechanism will be employed in an automatic screw machine, commonly having five spindles.
Other objects of the invention are attained by the provision of a machine into which is incorporated the improved mechanism hereof.